Open-hearth slag utilization



Patented Nov. 6 1934 UNITED 5 OPEN-HEARTH SLAG UTILIZATION James E. Lose and Ralph H. Watson, MunhalLPat No Drawing. Application November 14, 1932,

Serial No. 642,679

3 Claims. (Cl. 76)

This invention is a method of utilizing basic the blast-furnace may be an iron of the following open-hearth slag by the recovery of relatively constituents: large amounts of its manganese, phosphorus and Per Per iron cent cent The method is particularly characterized in fifg i g "i t so that the slag forms the metal producing burden silicopn 63 of a blast-furnace without necessarily the addi sul y- 5&5 mm O 3 tion of ore, scrap, etc. The slag is charged n C I the furnace along with fuel and, if necessary, a M on Tom to suitable fluXing ma siliceous material may This blast-furnace product may be called phos- 65 also be added, depending upon the desired silicon pho spiegel and in the case of a basic opemhearth content 015 the i to be Although or electric furnace may be charged along with hlgh or low phosphorus 5111090115 iron, roll scale and other iron oxides. These ganlfe o 0TB may be used: 1t Should not oxidize the manganese and silicon, when the m prise the major The above op nese, high phos a basic furnace or converter ganese so that a nose for use as spieg phorus content.

This high phosphorus iron i in a basic furnace or conver phosphorus so that a sults. The metal pro or'a steel which may be used treatment except for deoxidation, these depending on whether the furnace or the form of phosphoric acid soluble in citric acid or fertilization purposes in should, of course, be mixe to furnish the needed elements fertilized.

The open-hearth present method may charged from a b lowing:

Iron

Manganese Phosphorus Silica Alumina Lime Magnesia portion of the burden. eration produces a high mangaphorus iron which is treated in high manganese slag results which may be smelted to produce ferro-mangael. The metal produced is an iron of rather low manganese and high phoster to oxidize the high phosphorus slag reduced is either a semisteel which may be converted in an open-hearth slag to be treated by the be that ordinarily disasic furnace and have the conventional range of constituents, such as the fol- The product of the above after treatment in oxidize the man- 6% it has been found that the phosphorus beenreduced to from 05% to 3%.

The slag produced by this openment may have a composition as follows:

s further treated Per with further PhOSPhOIllS from 0,05 to Iron from 3.0 to

converter is used.

Per cent This slag Silicon under t t 11 t be Carbon from 2.0 to

As stated, the above slag has a manganese content high enough to be used as a burden for a ferro-manganese furnace or for spiegel.

Per cent Per cent from 18.0 to

from 5.0 to from 0.3 to from 15.0 to from 2.0 to from 20.0 to from 4.0 to

phosphorus oxi cient extent, below 3%, the furnac metal is at a high temperature, so they enter the slag. When the manganese is reduced to a sufficient extent, for instance under 1%, carbon is added to the slag in the furnace to decrease the phosphorus and iron oxide. This carbon may be coke or coal thrown on the slag in a layer. When the iron oxide has been reduced to about 4 to hearth treatcent Mang,anese from 35.0 to 5 has Per cent The iron produced at this time may have a Per cent Manganese from 1.0 to 4.0 Phosphorus from 1.5 to

The iron obtained by this open-hearth treatment may be subjected to further treatment in the same furnace or removed to another basic open-hearth or electric furnace, the latter probably being preferable in most instances. During this second basic furnace treatment iron ore, roll scale, etc. and lime is added to the metal while at a comparatively low temperature, so that the dizes and enters the slag. When the metals phosphorus content reduces to a sume is tapped and the slag separated from the iron. The iron of a semi-steel of the Percent Carbon 2.00 Manganese 1.70 Phosphorus 0.30 Sulphur 0.01 Silicon 0.01.

The treatment may also be effected by a basic Bessemer converter either entirely or at different stages. That is to say, the metal produced at one stage by the basic furnace might be further treated by a basic converter, or vice versa.

The method will now be disclosed when a Bessemer converter is used.

The phospho-spiegel produced from the blastfurnace is transferred to a basic converter and blown with air. The manganese, silicon and some iron oxidizes and raises the temperature to a high degree, so that little phosphorus is oxidized and enters the slag. When the manganese content of the metal is reduced to a sufficient degree, under 1%, the phosphorus and iron oxide in the slag should be low. If the iron oxide is not sufficiently low, carbon may be added. This reduces the iron oxide and the phosphorus. The converter is then tapped and the metal and slag separated by pouring or teeming. This metal and. slag will have substantially the same constituents as that produced by the basic furnace procedure. The slag produced will be used for its manganese content, as has been previously described.

To effect the recovery of the iron and phosphorus the metal produced by the converter may be blown according to the usual basic Bessemer practice so that the remaining manganese, carbon and phosphorus are consecutively oxidized. The metal left may be classed as steel, while the slag contains the manganese and phosphorus. This slag may be used for fertilization purposes in the manner previously suggested.

If the last mentioned Bessemer blow is conducted so that oxidation of the phosphorus occurs at a low temperature the carbon may not be properly oxidized. The addition of roll scale and lime in sufficient quantities will assure almost complete oxidation of the phosphorus and the retention of most of the carbon in the iron so that it may be used in an open-hearth to produce acceptable steel.

The slag produced by either the basic furnace or converter procedures and which is to be used for fertilization purposes will be of substantially the following composition:

Range Typical Per- Per- Percent cent cent From 2.0to 6.0 4.0 Alumina From 1.0 to 2.0 1. 4 Lime From 40.0 to 50.0 45.8 Magnesia From 1.0 to 5.0 1.9 Mang. oxide From 10.0 to 20. 0 14. 2 Ferrous oxide From 5.0 to 10.0 6. 9 Phosphoric acid From 18.0 to 30.0 24. 9 S01. phos. acid 22. 6

In the above analysis it is to be noted that the phosphorus is relatively high and the silica relatively low.

We claim:

1. The method of utilizing basic open-hearth furnace slag by smelting it in the presence of a reducing agent to obtain a high manganese and phosphorus product and treating this product in a basic converter to obtain a high manganese slag and a high phosphorus slag.

2. The method of utilizing basic open-hearth furnace slag by smelting it in the presence of a reducing agent to obtain a high manganese and phosphorus iron, and treating said iron in a basic converter to oxidize the manganese therein to produce a high manganese slag and a high phosphorus iron, and treating said high phosphorus iron in a basic converter to oxidize the phosphorus to produce a high phosphorus slag.

3. The method of utilizing basic open-hearth furnace slag by smelting it in the presence of a reducing agent to obtain a high manganese and phosphorus product, oxidizing this product in a basic converter so as to produce a high manganese, low phosphorus slag and a low manganese, high phosphorus iron and oxidizing said 10w manganese, high phosphorus iron in a basic converter to produce a usable metal and a high phosphorus slag.

JAMES E. LOSE. RALPH H. WATSON. 

